To guarantee that sufficient bandwidth is available to a virtual machine, vSphere implements admission control at host and cluster levels based on bandwidth reservation and teaming policy.

Bandwidth Admission Control in vSphere Distributed Switch

When you power on a virtual machine, the Network I/O Control feature on a distributed switch verifies that these conditions are satisfied on the host.

  • A physical adapter on the host can supply the minimum bandwidth to the VM network adapters in accordance with the teaming policy and reservation.

  • The reservation for a VM network adapter is less than the free quota in the network resource pool.

If you change the reservation for a network adapter of a running virtual machine, Network I/O Control verifies again whether the associated network resource pool can accommodate the new reservation. If the pool does not have enough unclaimed quota, the change is not applied.

To use admission control in vSphere Distributed Switch, perform the following tasks:

  • Configure bandwidth allocation for the virtual machine system traffic on the distributed switch.

  • Configure a network resource pool with a reservation quota from the bandwidth configured for virtual machine system traffic.

  • Associate the network resource pool with the distributed port group that connects the virtual machines to the switch.

  • Configure the bandwidth requirements of a virtual machine connected to the port group.

Bandwidth Admission Control in vSphere DRS

If you power on a virtual machine that is in a cluster, vSphere DRS places the virtual machine on a host that has the capacity to guarantee the bandwidth reserved for the virtual machine according to the active teaming policy.

vSphere DRS migrates a virtual machine to another host to satisfy the bandwidth reservation of the virtual machine in these situations:

  • The reservation is changed to a value that the initial host can no longer satisfy.

  • A physical adapter that carries traffic from the virtual machine is offline.

To use admission control in vSphere DRS, perform the following tasks:

  • Configure bandwidth allocation for the virtual machine system traffic on the distributed switch.

  • Configure the bandwidth requirements of a virtual machine that is connected to the distributed switch.

For more information about resource management according to bandwidth demands of virtual machines, see the vSphere Resource Management documentation.

Bandwidth Admission Control in vSphere HA

When a host fails or is isolated, vSphere HA powers on a virtual machine on another host in the cluster according to the bandwidth reservation and teaming policy.

To use admission control in vSphere HA, perform the following tasks:

  • Allocate bandwidth for the virtual machine system traffic.

  • Configure the bandwidth requirements of a virtual machine that is connected to the distributed switch.

For more information about vSphere HA provides failover based on the bandwidth demands of virtual machines, see the vSphere Availability documentation.